This invention relates to prosthetic knee joints, and more particularly to improved prosthetic knee joints, which emulate the operation of a normal knee with little friction for prolonging the life of the artificial knee.
Conventional movement in a healthy human knee joint involves complex movements of the femur, the tibia, and the patella. In flexion, the distal end of the femur and the proximal end of the tibia rotate and glide relative to one another with the center of rotation of the joint moving posteriorly over the condyles of the femur. In extension, the reverse of the aforesaid movement takes place. Simultaneously therewith, the patella or kneecap moves over the femoral condyles while remaining at a relatively constant distance from the tubercle of the tibia via the patella ligament attached to the patella.
Numerous attempts have been made to produce prosthetic knee joints which emulate the complex aforesaid knee function with somewhat limited success. The proposed joints with their contact and bearing surfaces produce restricted movements, suffer from wear and tear, shed debris, provide improper support of the bones involved causing bone deterioration, wear out, etc. Probably the biggest drawback of the prosthetic knee joint is that the breakdown of the joint most commonly due to bearing surface wear, regardless of the cause, results in the requirement of major surgery to replace the prosthetic joint. Prosthetic knees do not lend themselves to minor surgery for repair or replacement, which is costly and limits their use. The average life of prosthetic knees is ten to fifteen years.